A hydraulic accumulator comprises two-half shells, the diaphragm therebetween defining two cavities. One cavity contains pressurized gas and the cavity receives hydraulic fluid under pressure. The two-half shells are held together by a mechanical element, such as a belt which has been previously prestressed...http://www.google.com/patents/US4603711?utm_source=gb-gplus-sharePatent US4603711 - Prestressed hydraulic accumulator
